All the resignations will be effective once they have been accepted by congress.

Sequential killings

The political scandal began when three El Salvadorean parliamentarians and their driver were found shot dead in their car in an area east of the country's capital Guatemala City on February 19.

Four police officers arrested in connection with the killings were then murdered in the maximum security prison where they were being held six days later. Among those was the head of the squad that targets organised crime.

Vielmann had been under pressure to step down over the scandal. He had the backing of his president, but Berger had previously said the interior minister may have been required to take a lie detector test.

Elias Antonio Saca, the president of El Salvador, has reacted angrily to the case demanding a shake-up of the Guatemalan police system.

Javier Figueroa was one of the first
officials forced to quit over the killings [EPA]
Berger has urged his counterpart to not let "an isolated case" damage the normally good relations between the countries and to wait for the results of a government investigation.

The president cancelled a proposed visit to El Salvador last week.

Berger said last week that the fallout from the murders has "overwhelmed the advances achieved in these years of government."

Widening scandal

That has seen Javier Figueroa, the police detective in charge of the four men originally suspected of the murders, quit.

Last week a judge ordered the arrest of 24 employees of the maximum security El Boqueron prison where the four police officers subsequently had their throats slit.

Opposition figures including Alavaro Colom, currently leading polls for a presidential election to be held in September, say armed groups working within the police have been given free rein to carry out killings and to smuggle drugs, weapons and people.

Otto Perez Molina, a former military intelligence chief and another presidential candidate currently polling second behind Colom has described the situation as "anarchy".

Among the El Salvadorean politicians that were killed was Eduardo D'Aubuisson, the son of the late Roberto D'Aubuisson, an army major accused of masterminding the assassination in 1980 of the popular archbishop Oscar Arnulfo Romero.